7-amino-6-fluoro- and 7-amino-6,8-difluoro quinolone-3-carboxylic acids and 7-amino-6-fluoro-1,8-naphthyridine-3-carboxylic acids are especially known to have potent antibacterial activity especially in vitro against gram-negative bacteria. Corresponding 7-amino-pyrrolidinyl-quinolones and naphthyridines of the above type have shown to extend this potent activity against gram-positive bacteria. Nevertheless, many of the above compounds do not exhibit potent activity when tested in vivo. It has now been found that by adding an .alpha.-amino acid to the known 7-amino substituents, there is surprisingly enhanced in vivo antibacterial activity when such compounds are administered both orally and subcutaneously.